Despite its critical importance in visual function, maintenance of corneal integrity and ocular comfort, the dynamic variation of the tear film and tear meniscus (tear dynamics) remains one of the most neglected components of the eye. This neglect is due in large part to the extreme difficulty of quantitatively measuring the tears over the ocular surface since they keep changing during blinks. The purpose of this proposal is to develop a highly innovative, rapidly measured and comprehensive metric of tear quality and quantity that has a potentially high impact on a wide range of tear film studies. The metric to be developed is based on a precise and rapidly repeated cross-section of the tear over the cornea and around the eyelids, using a newly developed real-time optical coherence tomographer (OCT). The dynamic variation of the tear film thickness and tear menisci around the both eyelids has been successfully demonstrated for the first time, in normal subjects, to provide a full description of the tear dynamics. We hypothesize that this method will also provide reliable information on the characterization of the tear dynamics in the most challenging cases, such as elderly people or patients with dry eye syndrome who have difficulty with fixation, oculomotor stabilization and blink suppression (SA1). Our experiments will test and validate this method in normal and challenging subjects to characterize the tear dynamics and their relations with commonly used tear tests (such as tear breakup time and Schirmer's test). Development of this novel benchmark will have a high impact on further studies, for instance, to evaluate the effect of the tear dynamics on optical aberrations and ocular comfort, and to develop new approaches to the diagnosis and treatments of abnormalities of tearing (e.g. dry eye). [unreadable] [unreadable]